Elon Musk is known for founding automaker Tesla and Space Exploration Technologies Corp. (SpaceX), but recently he has set up the Flat Earth Society for such a burn, it could be his greatest achievement yet.

The Flat-Earthers actually believe Earth is a flat disc and everything that suggests otherwise is a conspiracy, created by NASA and other government agencies. On Tuesday, billionaire investor, engineer, and inventor Elon Musk asked them a somewhat philosophical question on Twitter, wondering why there isn’t a Flat Mars Society. To his and everybody else’s surprise (and amusement), the official Twitter account of the Flat Earth Society responded. Scroll down to read the hilarious exchange!